William Overall Yager (April 3, 1833 – January 20, 1904) was, during the American Civil War, initially the major and commanding officer of Yager's Third Battalion Texas Mounted Volunteers, and then later, as colonel and commanding officer of the First Texas (Yager's) Cavalry (CSA), and, in postwar years, member of the Virginia House of Delegates and the Senate of Virginia, Superintendent of Schools, and Treasurer for Page County, Virginia.